Structure and formation method of semiconductor device structure

ABSTRACT

Structures and formation methods of a semiconductor device structure are provided. The method includes forming a dielectric layer over a semiconductor substrate. The method also includes forming an opening in the dielectric layer. A dielectric constant of a first portion of the dielectric layer is less than that of a second portion of the dielectric layer surrounding the opening. The method further includes forming a conductive feature in the opening. The second portion is between the first portion and the conductive feature. In addition, the method includes modifying an upper portion of the first portion to increase the dielectric constant of the upper portion of the first portion. The method also includes removing the upper portion of the first portion and the second portion.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapidgrowth. Technological advances in IC materials and design have producedgenerations of ICs. Each generation has smaller and more complexcircuits than the previous generation.

In the course of IC evolution, functional density (i.e., the number ofinterconnected devices per chip area) has generally increased whilegeometric size (i.e., the smallest component (or line) that can becreated using a fabrication process) has decreased. This scaling-downprocess generally provides benefits by increasing production efficiencyand lowering associated costs.

However, these advances have increased the complexity of processing andmanufacturing ICs. Since feature sizes continue to decrease, fabricationprocesses continue to become more difficult to perform. Therefore, it isa challenge to form reliable semiconductor devices at smaller andsmaller sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It shouldbe noted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1A-1G are cross-sectional views of various stages of a process forforming a semiconductor device structure, in accordance with someembodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the subject matterprovided. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Some embodiments of the disclosure are described. FIGS. 1A-1G arecross-sectional views of various stages of a process for forming asemiconductor device structure, in accordance with some embodiments.Additional operations can be provided before, during, and/or after thestages described in FIGS. 1A-1G. Some of the stages that are describedcan be replaced or eliminated for different embodiments. Additionalfeatures can be added to the semiconductor device structure. Some of thefeatures described below can be replaced or eliminated for differentembodiments.

As shown in FIG. 1A, a semiconductor substrate 100 is provided. In someembodiments, the semiconductor substrate 100 is a bulk semiconductorsubstrate, such as a semiconductor wafer. For example, the semiconductorsubstrate 100 is a silicon wafer. The semiconductor substrate 100 mayinclude silicon or another elementary semiconductor material such asgermanium. In some other embodiments, the semiconductor substrate 100includes a compound semiconductor. The compound semiconductor mayinclude silicon germanium, gallium arsenide, silicon carbide, indiumarsenide, indium phosphide, another suitable compound semiconductor, ora combination thereof.

In some embodiments, the semiconductor substrate 100 includes asemiconductor-on-insulator (SOI) substrate. The SOI substrate may befabricated using a wafer bonding process, a silicon film transferprocess, a separation by implantation of oxygen (SIMOX) process, anotherapplicable method, or a combination thereof.

In some embodiments, isolation features (not shown) are formed in thesemiconductor substrate 100. The isolation features are used to defineactive regions and electrically isolate various device elements formedin and/or over the semiconductor substrate 100 in the active regions. Insome embodiments, the isolation features include shallow trenchisolation (STI) features, local oxidation of silicon (LOCOS) features,other suitable isolation features, or a combination thereof.

Examples of the various device elements, which may be formed in thesemiconductor substrate 100, include transistors, diodes, anothersuitable element, or a combination thereof. For example, the transistorsmay be metal oxide semiconductor field effect transistors (MOSFET),complementary metal oxide semiconductor (CMOS) transistors, bipolarjunction transistors (BJT), high voltage transistors, high-frequencytransistors, p-channel and/or n channel field effect transistors(PFETs/NFETs), etc. Various processes are performed to form the variousdevice elements, such as deposition, etching, implantation,photolithography, annealing, planarization, another applicable process,or a combination thereof.

In some embodiments, an interconnection structure is formed on thesemiconductor substrate 100. The interconnection structure includes aninterlayer dielectric layer (ILD) 110 and multiple conductive featuresincluding conductive features 120 in the interlayer dielectric layer110. The conductive features 120 may include conductive lines,conductive vias, and/or conductive contacts. In some embodiments, theinterlayer dielectric layer 110 includes multiple dielectric sub-layers.Multiple conductive features such as conductive contacts, conductivevias, and conductive lines are formed in the interlayer dielectric layer110.

In some embodiments, the interlayer dielectric layer 110 is made ofsilicon oxide, borosilicate glass (BSG), phosphoric silicate glass(PSG), borophosphosilicate glass (BPSG), fluorinated silicate glass(FSG), porous dielectric material, another suitable low-k dielectricmaterial, or a combination thereof. In some embodiments, the conductivefeatures 120 are made of copper, aluminum, gold, titanium, cobalt,tungsten, another suitable conductive material, or a combinationthereof. Various processes, including deposition, etching,planarization, or the like, may be used to form the interlayerdielectric layer 110 and the conductive features 120.

Afterwards, one or more dielectric layers and conductive features areformed on the interlayer dielectric layer 110 and the conductivefeatures 120 to continue the formation of the interconnection structure.Various device elements are interconnected through the interconnectionstructure over the semiconductor substrate 100 to form integratedcircuit devices. For example, one of the conductive features 120 may beelectrically connected to a doped region formed in the semiconductorsubstrate 100 through some of the conductive features includingconductive vias, conductive lines, and/or conductive contacts. Theintegrated circuit devices include logic devices, memory devices (e.g.,static random access memories, SRAMs), radio frequency (RF) devices,input/output (I/O) devices, system-on-chip (SoC) devices, image sensordevices, other applicable types of devices, or a combination thereof.

As shown in FIG. 1A, an etch stop layer 130 is deposited over theinterlayer dielectric layer 110 and the conductive features 120, inaccordance with some embodiments. The etch stop layer 130 is used toprotect the conductive features 120 from damage during subsequentprocesses for forming openings.

In some embodiments, the etch stop layer 130 is made of silicon carbide(SiC), silicon carbo-nitride (SiCN), silicon oxycarbide (SiCO), siliconnitride (SiN), silicon oxynitride (SiON), metal oxide, metal nitride,another suitable material, or a combination thereof. In someembodiments, the etch stop layer 130 is deposited using a chemical vapordeposition (CVD) process, a spin-on process, another applicable process,or a combination thereof. Embodiments of the disclosure are not limitedthereto. In some other embodiments, the etch stop layer 130 is notformed.

As shown in FIG. 1A, a dielectric layer 140 is deposited over the etchstop layer 130, in accordance with some embodiments. The dielectriclayer 140 may serve as an inter-metal dielectric (IMD) layer. In someembodiments, the dielectric layer 140 is made of a low-k dielectricmaterial. The low-k dielectric material has a smaller dielectricconstant than that of silicon dioxide. For example, the low-k dielectricmaterial has a dielectric constant in a range from about 1.2 to about3.5.

As the density of semiconductor devices increases and the size ofcircuit elements becomes smaller, the resistance capacitance (RC) delaytime increasingly dominates circuit performance. Using a low-kdielectric material as the dielectric layer 140 is helpful for reducingthe RC delay.

In some embodiments, the dielectric layer 140 includes acarbon-containing material. For example, the dielectric layer 140includes SiOC, SiCOH, SiOCN, or a combination thereof. In someembodiments, the dielectric layer 140 is made of carbon-doped siliconoxide. The carbon-doped silicon oxide may also be referred to asorganosilicate glass (OSG) or C-oxide. In some embodiments, thecarbon-doped silicon oxide includes methyl silsesquioxane (MSQ),hydrogen silsesquioxane (HSQ), polysilsesquioxane, another suitablematerial, or a combination thereof. In some embodiments, the dielectriclayer 140 is deposited using a CVD process, a spin-on process, a spraycoating process, another applicable process, or a combination thereof.

Afterwards, openings are formed in the dielectric layer 140. In someembodiments, the openings include trenches, via holes, or a combinationthereof. As shown in FIG. 1B, some of the trenches (such as openings150A, 150B, and 150C) and some of the via holes (such as an opening 160)are formed, in accordance with some embodiments.

The opening 150A is located laterally between the opening 150B and theopening 150C. The opening 150A is separated from the opening 150B by adistance D₁. The opening 150A is separated from the opening 150C by adistance D₂. In some embodiments, the distance D₁ is less than thedistance D₂. In some embodiments, the distance D₁ is in a range fromabout 1 nm to about 30 nm.

Many variations and/or modifications can be made to embodiments of thedisclosure. In some other embodiments, the distance D₁ is equal to thedistance D₂.

In some embodiments, the dielectric layer 140 is a single layer. Thereis no etch stop layer lining the bottom surface of the openings 150A,150B, and 150C.

In some embodiments, the opening 150A and the opening 160 are connectedto each other and together penetrate the dielectric layer 140. In someembodiments, the opening 160 extends from the bottom surface of theopening 150A. In some embodiments, the opening 160 exposes a portion ofthe etch stop layer 130. In some other embodiments, the opening 160exposes one of the conductive features 120.

As shown in FIG. 1B, the opening 150A is wider than the opening 160 asviewed from a cross-sectional view, in accordance with some embodiments.The cross-sectional view may be taken along a plane that isperpendicular to the main surface of the semiconductor substrate 100. Insome other embodiments, the opening 150A and the opening 160 have thesame width as viewed from the cross-sectional view.

In some embodiments, the openings 150A, 150B, 150C, and 160 are formedusing multiple photolithography processes and etching processes. In someembodiments, the opening 160 is formed before the formation of theopenings 150A, 150B, and 150C. For example, the openings 150A, 150B,150C, and 160 are formed using a “via first” process. In some otherembodiments, the openings 150A, 150B, and 150C are formed before theformation of the opening 160. For example, the openings 150A, 150B,150C, and 160 are formed using a “trench first” process.

As shown in FIG. 1B, multiple portions 140A and 140B are formed in thedielectric layer 140, in accordance with some embodiments. The portions140A are between some of the dense openings while the portions 140B arebetween some of the sparse openings. In some embodiments, the portions140A surround some of the dense openings, and the portions 140B surroundsome of the sparse openings. For example, one or some of the portions140A are within a region with the distance D₁ and between the opening150A and the opening 150B. One or some of the portions 140B are within aregion with the distance D₂ and between the opening 150A and the opening150C.

In some embodiments, the portions 140A have different dielectricconstants than that of a first portion P₁ of the dielectric layer 140which adjoins the portions 140A. In some embodiments, the portions 140Bhave different dielectric constants than that of a second portion P₂ ofthe dielectric layer 140 which adjoins the portions 140B. For example,the dielectric constant of the portions 140A and 140B is greater thanthat of the first portion P₁ and the second portion P₂.

Interfaces between the portions 140A and the first portion P₁ andbetween the portions 140B and the second portion P₂ may be observedusing a spectrometer. These interfaces are shown by dotted lines infigures. In some embodiments, the spectrometer is an electron energyloss spectrometer (EELS), or another suitable spectrometer.

In some embodiments, the first portion P₁ and the second portion P₂include a carbon-containing dielectric material. The carbon-containingdielectric material of the first portion P₁ and the second portion P₂may include SiOC_(x) (0<x≦2), SiC_(x)OH (0<x≦3), SiOC_(x)N (0<x≦1),another suitable dielectric material, or a combination thereof.

In some embodiments, the portions 140A and 140B include acarbon-containing dielectric material. In some embodiments, the carbonconcentration of the portions 140A and 140B is different from that ofthe first portion P₁ and the second portion P₂. For example, the carbonconcentration of the portions 140A and 140B is less than that of thefirst portion P₁ and the second portion P₂. A spectrometer, such as anEELS, may be used to measure carbon concentration. In some embodiments,the carbon-containing dielectric material of the portions 140A and 140Binclude SiOC_(x-y) (0<y<x), SiC_(x-y)OH (0<y<x), SiOC_(x-y)N (0<y<x),another suitable dielectric material, or a combination thereof.

In some embodiments, the portions 140A between the opening 150A and theopening 150B are connected with each other. As a result, a top surfaceS₁ of the first portion P₁ is covered by the portions 140A. In someembodiments, the top surface S₁ is non-coplanar with a top surface S₂ ofthe second portion P₂, as shown in FIG. 1B.

Embodiments of the disclosure are not limited thereto. In some otherembodiments, some of the portions 140A between the opening 150A and theopening 150B are separated from each other. As a result, the top surfaceS₁ of the first portion P₁ is substantially coplanar with the topsurface S₂ of the second portion P₂.

In some embodiments, the portions 140B between the opening 150A and theopening 150C are separated from each other by the second portion P₂. Insome other embodiments, the portions 140B between the opening 150A andthe opening 150C are connected with each other.

In some embodiments, the sidewalls and the bottom surface of the opening150A are lined with one of the portions 140A and one of the portions140B. In some embodiments, one of the portions 140A and one of theportions 140B further extends along the sidewalls of the opening 160. Insome embodiments, one of the portions 140A and one of the portions 140Btogether continuously surround the opening 150A and the opening 160.

In some embodiments, the sidewalls of the opening 150B are lined withsome of the portions 140A. In some embodiments, the bottom surface ofthe opening 150B is substantially not surrounded by the portions 140A.In some other embodiments, the bottom surface of the opening 150B islightly lined with some of the portions 140A. In some embodiments, someof the portions 140B continuously surround the sidewalls and the bottomsurface of the opening 150C.

In some embodiments, some surface portions of the dielectric layer 140are exposed through the openings 150A, 150B, 150C, and 160, and aremodified and transformed into the portions 140A and 140B. As a result,the portions 140A and 140B extend from the exposed surfaces of thedielectric layer 140 towards the interior of the dielectric layer 140.In some embodiments, some surface portions of the dielectric layer 140,which are exposed through the openings 150A, 150B, 150C, and 160, aredamaged and are transformed into the portions 140A and 140B.

In some embodiments, the portions 140A and 140B are formed during theformation of the openings 150A, 150B, 150C, and 160 or by performinganother suitable process. In some embodiments, the portions 140A and140B are formed due to one or more etching processes for forming theopenings 150A, 150B, 150C, and 160. In some embodiments, the portions140A and 140B are formed due to the removal of one or more mask layersused in one or more etching processes for forming the openings 150A,150B, 150C, and 160.

In some embodiments, the portions 140A and 140B are formed due to anetching process and the removal of a mask layer. In some embodiments,the etching process and/or the removal of the mask layer include aplasma-involved process.

In some embodiments, the dielectric constant of the exposed surfaceportions of the dielectric layer 140 is changed during the formation ofthe openings 150A, 150B, 150C, and 160. In some embodiments, thedielectric constant of the exposed surface portions of the dielectriclayer 140 is increased after the portions 140A and 140B are formed. As aresult, the dielectric constant of the portions 140A or 140B is greaterthan that of the first portion P₁ or the second portion P₂.

In some embodiments, the carbon concentration of the exposed surfaceportions of the dielectric layer 140 is changed during the formation ofthe openings 150A, 150B, 150C, and 160. In some embodiments, the carbonconcentration of the exposed surface portions of the dielectric layer140 is reduced after the portions 140A and 140B are formed. As a result,the carbon concentration of the portions 140A and 140B is less than thatof the first portion P₁ and the second portion P₂.

As shown in FIG. 1C, a portion of the etch stop layer 130 exposed fromthe opening 160 is removed, in accordance with some embodiments. As aresult, one of the conductive features 120 is partially exposed from theopening 160.

Afterwards, conductive features are formed in the openings of thedielectric layer 140, in accordance with some embodiments. In someembodiments, the conductive features include conductive lines,conductive vias, or a combination thereof. The conductive lines areformed in the trenches, and the conductive vias are formed in the viaholes. Each of the conductive features in the openings of the dielectriclayer 140 is electrically connected to one of the conductive features120.

As shown in FIG. 1C, some of the conductive lines (such as conductivefeatures 170A, 170B, and 170C) and some of the conductive vias (such asa conductive feature 180) are formed. The conductive features 170A,170B, and 170C are respectively formed in the openings 150A, 150B, and150C. The conductive feature 180 is formed in the opening 160 and iselectrically connected to one of the conductive features 120.

One or each of the conductive features 170A, 170B, and 170C has a widthW₁. In some embodiments, the width W₁ is equal to the distance D₁between the conductive features 170A and 170B. In some otherembodiments, the width W₁ is less than the distance D₁. In some otherembodiments, the width W₁ is greater than the distance D₁. In someembodiments, the width W₁ is referred to as the minimum line width. Insome embodiments, the distance D₁ is equal to the minimum line width. Insome embodiments, the distance D₂ between the conductive features 170Aand 170C is greater than the minimum line width.

The conductive feature 170A has a top surface S₃ and a bottom surfaceS₄. The conductive feature 180 extends from the bottom surface S₄ to oneof the conductive features 120. In some embodiments, the top surface S₃is non-coplanar with the top surface S₁ of the first portion P₁ of thedielectric layer 140. In some embodiments, the top surface S₁ is lowerthan the top surface S₃ and is higher than the bottom surface S₄. Insome embodiments, the top surface S₃ is closer to the top surface S₁than the bottom surface S₄. In some embodiments, the top surface S₃ issubstantially coplanar with the top surface S₂ of the second portion P₂of the dielectric layer 140.

In some embodiments, one of the portions 140A and one of the portions140B gradually become narrower along a direction from the top surface S₃of conductive feature 170A towards the bottom surface S₄ of conductivefeature 170A. In some embodiments, one of the portions 140A and one ofthe portions 140B gradually become narrower along the direction from thetop surface of the conductive feature 180 towards the bottom surface theconductive feature 180. In some embodiments, one of the portions 140Aand one of the portions 140B gradually become narrower along thedirection from the top surface S₃ of conductive feature 170A towards thebottom surface the conductive feature 180.

In some embodiments, the conductive features 170A and 180 are in directcontact with the portions 140A and 140B. In some embodiments, theconductive feature 170B is in direct contact with the portions 140A. Insome embodiments, the conductive feature 170C is in direct contact withthe portions 140B.

Embodiments of the disclosure are not limited thereto. In some otherembodiments, one or more of the conductive features 170A, 170B, and 180are not in direct contact with the portions 140A. In some otherembodiments, one or more of the conductive features 170A, 170C, and 180are not in direct contact with the portions 140B.

In some embodiments, one of the portions 140A is sandwiched between thefirst portion P₁ of the dielectric layer 140 and the conductive feature170A or 170B. In some embodiments, one of the portions 140B issandwiched between the second portion P₂ of the dielectric layer 140 andthe conductive feature 170A or 170C.

In some embodiments, the conductive features 170A, 170B, 170C, and 180are made of copper, aluminum, tungsten, titanium, nickel, gold,platinum, silver, another suitable material, or a combination thereof.Each of the conductive features 170A, 170B, 170C, and 180 may be asingle layer or have multiple stacked layers.

In some embodiments, one or more conductive material layers aredeposited over the dielectric layer 140 to fill the openings 150A, 150B,150C, and 160. In some embodiments, the one or more conductive materiallayers are deposited using an electroplating process, a PVD process, aCVD process, an electroless plating process, another applicable process,or a combination thereof.

Afterwards, a planarization process is used to remove the conductivematerial layers outside of the openings 150A, 150B, 150C, and 160. Theplanarization process may include a chemical mechanical polishing (CMP)process, a dry polishing process, a grinding process, an etchingprocess, another applicable process, or a combination thereof. As aresult, the remaining portions of the conductive material layers in theopenings 150A, 150B, and 150C, form the conductive features 170A, 170B,and 170C. The remaining portions of the conductive material layers inthe opening 160 form the conductive feature 180.

In some other embodiments, before the conductive material layers aredeposited, a barrier layer (not shown) is formed over the dielectriclayer 140 and over the sidewalls and the bottom surfaces of the openings150A, 150B, 150C, and 160. For example, the barrier layer is conformallydeposited over the dielectric layer 140 and in the openings 150A, 150B,150C, and 160. After the planarization process for forming theconductive features 170A, 170B, 170C, and 180, the barrier layer on thetop surface of the dielectric layer 140 is also removed. As a result,the conductive features 170A, 170B, 170C, and 180 are separated from theportions 140A and 140B by the barrier layer.

The barrier layer can protect the dielectric layer 140 from diffusion ofa metal material from the conductive features 170A, 170B, 170C, and 180.In some embodiments, the barrier layer includes multiple sub-layersincluding a glue layer (not shown). The glue layer may be used toimprove adhesion between the barrier layer and a subsequently formedlayer.

In some embodiments, the barrier layer is made of tantalum nitride,titanium nitride, tungsten nitride, another suitable material, or acombination thereof. The glue layer may be made of tantalum, titanium,another suitable material, or a combination thereof. In someembodiments, the barrier layer is deposited using a PVD process, a CVDprocess, another applicable process, or a combination thereof. Manyvariations and/or modifications can be made to embodiments of thedisclosure. In some other embodiments, the barrier layer is not formed.

As shown in FIG. 1D, a patterned mask layer 190 is formed over thedielectric layer 140, in accordance with some embodiments. The patternedmask layer 190 is used to assist in a subsequent treatment.

In some embodiments, the patterned mask layer 190 has an openingexposing a region where dense conductive features are located. Anotherregion where sparse conductive features are located is covered by thepatterned mask layer 190. For example, a region between the conductivefeatures 170A and 170B is exposed from the opening of the patterned masklayer 190. Another region between the conductive features 170A and 170Care covered by the patterned mask layer 190. As a result, the portions140A are exposed from the opening of the patterned mask layer 190 whilethe portions 140B are covered by the patterned mask layer 190.

Many variations and/or modifications can be made to embodiments of thedisclosure. In some other embodiments, a region where dense conductivefeatures are located and another region where some sparse conductivefeatures are located are exposed from the opening of the patterned masklayer 190. Another region where some other sparse conductive featuresare located is covered by the patterned mask layer 190.

In some embodiments, the conductive feature 170A is covered by thepatterned mask layer 190. The conductive feature 170B closer to theconductive feature 170A is exposed from the opening of the patternedmask layer 190 while the conductive feature 170C farther from theconductive feature 170A is covered by the patterned mask layer 190. Insome other embodiments, the conductive feature 170B is also covered bythe patterned mask layer 190. Accordingly, the conductive feature 170Bmay be prevented from being damaged during subsequent processes.

Many variations and/or modifications can be made to embodiments of thedisclosure. In some other embodiments, the conductive feature 170A isexposed from the opening of the patterned mask layer 190. One or more ofthe portions 140B between the conductive features 170A and 170C are alsoexposed from the opening of the patterned mask layer 190.

In some embodiments, the patterned mask layer 190 is a patternedphotoresist layer. For example, a photoresist layer is deposited overthe dielectric layer 140. Afterwards, the photoresist layer is patternedby one or more photolithography processes. As a result, the patternedmask layer 190 is formed.

In some other embodiments, the patterned mask layer 190 is made ofsilicon oxide, silicon nitride, another suitable material, or acombination thereof. For example, a mask material layer is depositedover the dielectric layer 140. A patterned photoresist is used as anetching mask to pattern the mask material layer. Afterwards, one or moreetching processes are used to transfer the pattern of the patternedphotoresist to the mask material layer. As a result, the patterned masklayer 190 is formed. The patterned photoresist is subsequently removed.

As shown in FIG. 1D, an upper portion of the first portion P₁ of thedielectric layer 140 is modified using a modification operation 192, inaccordance with some embodiments. As a result, the upper portion of thefirst portion P₁ that is modified and the portions 140A together form aportion 140A′, as shown in FIG. 1E in accordance with some embodiments.

In some embodiments, the second portion P₂ of the dielectric layer 140between the conductive features 170A and 170C is covered by thepatterned mask layer 190 and is not modified, as shown in FIGS. 1D and1E. Embodiments of the disclosure are not limited thereto. In some otherembodiments, the second portion P₂ is exposed from the opening of thepatterned mask layer 190 and is modified.

In some embodiments, a lower portion of the first portion P₁ isseparated from the conductive feature 180 by a portion of the portion140A′, as shown in FIG. 1E. In some embodiments, a distance D₃ betweenthe lower portion of the first portion P₁ and the conductive feature 180gradually becomes smaller along the direction from the top surface S₃towards the bottom surface S₄.

As shown in FIGS. 1D and 1E, the top surface S₁′ of the remainingportion of the first portion P₁ that is not modified is lower than thetop surface S₁ of the first portion P₁ before being modified, inaccordance with some embodiments. The top surface S₁′ may be a flatsurface, an uneven surface including a recess or protrusion, a curvedsurface, or a surface with another possible profile. An interfacebetween the portion 140A′ and the first portion P₁ may be observed usinga spectrometer, such as an EELS.

In some embodiments, the bottom surface S₄ of the conductive feature170A is closer to the top surface S₁′ than the top surface S₃ of theconductive feature 170A, as shown in FIG. 1E. In some embodiments, thetop surface S₁′ is lower than the top surface S₃ and is higher than thebottom surface S₄. In some other embodiments, the top surface S₁′ issubstantially coplanar with the bottom surface S₄.

In some embodiments, the upper portion of the first portion P₁ ismodified to be removable by an etchant used in a subsequent etchingprocess. In some embodiments, the upper portion of the first portion P₁is modified to have different dielectric constants than the lowerportion of the first portion P₁ (i.e., the remaining portion of thefirst portion P₁ that is not modified). For example, the dielectricconstant of the upper portion of the first portion P₁ becomes greaterthan the lower portion of the first portion P₁. In some embodiments, thedielectric constant of the upper portion of the first portion P₁ afterthe modification operation 192 is substantially equal to the dielectricconstant of the portions 140A and 140B.

In some embodiments, the carbon concentration of the upper portion ofthe first portion P₁ is changed due to the modification operation 192.In some embodiments, the upper portion of the first portion P₁ isoxidized. As a result, the carbon concentration of the upper portion ofthe first portion P₁ becomes less than that of the lower portion of thefirst portion P₁.

In some embodiments, the modification operation 192 is an ion treatmentand/or a plasma-involved process not involving ion bombardment. In someembodiments, the modification operation 192 includes anoxygen-containing plasma process or another suitable process. In someembodiments, the reaction gas used in the modification operation 192includes oxygen, nitrogen oxide, another suitable oxygen-containing gas,or a combination thereof. In some embodiments, the operation power usedfor performing the modification operation 192 is in a range from about10 W to about 150 W.

In some embodiments, the conditions of the modification operation 192are fine-tuned to modify the upper portion of the first portion P₁.Accordingly, the portions 140A and the first portion P₁ aresubstantially not removed.

In some embodiments, a remote plasma process is performed to provideplasma over the dielectric layer 140 and the patterned mask layer 190.The portions 140A and the first portion P₁ are not directly exposed toplasma. As a result, the portions 140A and the first portion P₁ aresubstantially not removed during the modification operation 192. Theconductive features 170A and 170B may also be prevented from damage dueto the remote plasma process.

In some embodiments, carbon in the upper portion of the first portion P₁is partially scavenged during the modification operation 192. Forexample, carbon in the upper portion of the first portion P₁ ispartially drawn out or depleted by oxygen ion in oxygen-containingplasma, another suitable ion, or a combination thereof. As a result, thecarbon concentration of the upper portion of the first portion P₁ isreduced after performing the modification operation 192.

In some embodiments, the upper portion of the first portion P₁ becomes acarbon-deficient dielectric material while the lower portion of thefirst portion P₁ is still made of a carbon-sufficient dielectricmaterial. The carbon-deficient dielectric material may includeSiOC_(x-z) (0<z<x), SiC_(x-z)OH (0<z<x), SiOC_(x-z)N (0<z<x), anothersuitable carbon-sufficient dielectric material, or a combinationthereof. The carbon concentration of the upper portion of the firstportion P₁ may be substantially equal to or different from that of theportions 140A and 140B.

In some embodiments, the top surface of the conductive feature 170B isexposed from the opening of the patterned mask layer 190, as shown inFIGS. 1D and 1E. The top surface of the conductive feature 170B may beoxidized during the modification operation 192. In some embodiments, aclean treatment is performed over the conductive feature 170B. In someembodiments, a solution is used to remove an oxidized portion of the topsurface of the conductive feature 170B. In some embodiments, a pH-valueof the solution is in a range from about 7 to about 9.

As shown in FIG. 1F, the portion 140A′ of the dielectric layer 140 isremoved, in accordance with some embodiments. As a result, the remainingportion of the first portion P₁ that is not modified by the modificationoperation 192 is exposed. In some embodiments, only a little of thedielectric layer 140 is left between the conductive features 170A and170B. In some other embodiments, there is substantially no dielectriclayer 140 left between the conductive features 170A and 170B.

As shown in FIG. 1F, the conductive features 170A, 170B, and 180, andthe remaining portion of the first portion P₁ together surround one ormore gaps including a gap 200, in accordance with some embodiments. Thegap 200 is used to provide further electrical isolation between theconductive features 170A and 170B. In some embodiments, the gap 200 isan air gap.

As shown in FIG. 1F, the gap 200 has a first portion G₁ and a secondportion G₂, in accordance with some embodiments. In some embodiments,the first portion G₁ has a width W₂ that is substantially equal to thedistance D₁ between the conductive features 170A and 170B. In someembodiments, the first portion G₁ is not thicker than the conductivefeatures 170A and 170B. In some embodiments, the first portion G₁extends along the conductive features 170A and 170B as viewed from a topview. The top view may be taken along a plane that is parallel to themain surface of the semiconductor substrate 100.

In some embodiments, the second portion G₂ is in communication with thefirst portion G₁ and vertically extends from the first portion G₁ alongthe conductive feature 180. In some embodiments, the second portion G₂is narrower than the first portion G₁. In some embodiments, the secondportion G₂ gradually becomes narrower along the direction from the topsurface S₃ towards the bottom surface S₄. In some other embodiments, alittle of the portion 140A′ is left between the first portion P₁ of thedielectric layer 140 and the conductive feature 180.

As shown in FIG. 1F, an etching process 194 is performed over thedielectric layer 140 and the patterned mask layer 190 to remove theportion 140A′, in accordance with some embodiments. Afterwards, thepatterned mask layer 190 is removed. In some embodiments, the etchingprocess 194 is a dry etching process, such as an isotropic etchingprocess.

In accordance with some embodiments, a vapor is used as an etchant inthe etching process 194. In some embodiments, the vapor includes a vaporcontaining HF, another suitable vapor, or a combination thereof. In someembodiments, the vapor substantially does not react with the conductivefeatures 170A and 170B. As a result, the sidewalls of the conductivefeatures 170A and 170B are prevented from being bombarded and damagedduring the removal of the portion 140A′.

In some embodiments, a dielectric material having a higher dielectricconstant is removable by the vapor while a dielectric material having alower dielectric constant is substantially not removable by the vapor.In some embodiments, a carbon-deficient dielectric material is removableby the vapor while a carbon-sufficient dielectric material issubstantially not removable by the vapor.

In some embodiments, the portion 140A′ is more susceptible to the vaporthan the remaining portion of the first portion P₁ that is not modifiedby the modification operation 192. In some embodiments, the vapor hassufficiently high etch selectivity of the portion 140A′ to theun-modified portion of the first portion P₁. Therefore, the vaporselectively removes the portion 140A′ and substantially does not reactwith the remaining portion of the first portion P₁.

In some embodiments, the portions 140B of the dielectric layer 140 arecovered by the patterned mask layer 190. The portions 140B are notmodified and removed. As a result, there is no gap, such as an air gap,in the dielectric layer 140 between conductive features 170A and 170C.Therefore, the dielectric layer 140 between conductive features 170A and170C provides a flat surface. The dielectric layer 140 also hassufficient structural strength to support layers and featuressubsequently formed over the dielectric layer 140.

Embodiments of the disclosure are not limited thereto. In some otherembodiments, one or more of the portions 140B are exposed from theopening of the patterned mask layer 190. Afterwards, the exposedportions 140B are removed, for example, by performing an etchingprocess. As a result, more gaps, such as air gaps, are formed in thedielectric layer 140 to provide enhanced electrical isolation betweenthe conductive features.

Many variations and/or modifications can be made to embodiments of thedisclosure. In some other embodiments, the upper portion of the firstportion P₁ is not modified and the portion 140A′ is not formed. In someembodiments, the portions 140A shown in FIG. 1C are directly removed byan etching process using a vapor as an etchant. In some embodiments, theportions 140B shown in FIG. 1C are also directly removed.

In some cases, a gap is formed in a dielectric layer by performing aplasma process. Some portions of the dielectric layer surrounding thegap may be bombarded with ions during the plasma process. Therefore, itis difficult to control the profile and size of the gap. The dielectriclayer with the gap may be insufficiently strong to support a conductivefeature surrounded by the gap.

In accordance with some embodiments, the conditions of the modificationoperation 192 can be fine-tuned to adjust the profile and size of theportion 140A′. The gap 200 is subsequently formed by removing theportion 140A′. Therefore, it can be ensured that the size of the gap 200can be as large as possible but the first portion G₁ of the gap 200 isnot thicker than the conductive features 170A and 170B. As a result,parasitic capacitance between the conductive lines is mitigated due tothe magnified gap 200. Also, the conductive features 170A and 170B aresufficiently supported by the dielectric layer 140.

As shown in FIG. 1G, an etch stop layer 210 is deposited over thedielectric layer 140 and the conductive features 170A, 170B, and 170C,in accordance with some embodiments. In some embodiments, the etch stoplayer 210 covers the gap 200 without filling it. In some otherembodiments, the etch stop layer 210 covers the gap 200 and slightlyextends into it without fully filling it.

Embodiments of the disclosure are not limited thereto. In some otherembodiments, the etch stop layer 210 conformally extends along thesidewalls and the bottom surface of the gap 200 without fully fillingit. In some embodiments, the gap 200 is not sealed by the etch stoplayer 210 conformally extending in the gap 200. In some otherembodiments, the gap 200 is sealed by the etch stop layer 210. The gap200 may be continuously and completely surrounded by the etch stop layer210.

The material and/or the formation method of the etch stop layer 210 aresimilar to or the same as those/that of the etch stop layer 130.However, many variations and/or modifications can be made to embodimentsof the disclosure. In some other embodiments, the etch stop layer 210 isnot formed.

As shown in FIG. 1G, a dielectric layer 220 is deposited over the etchstop layer 210, in accordance with some embodiments. In someembodiments, the dielectric layer 220 covers the gap 200 without fillingit. In some other embodiments, the dielectric layer 220 covers the gap200 and slightly extends into it without fully filling it. The materialand/or the formation method of the dielectric layer 220 are similar toor the same as those/that of the dielectric layer 140.

In some embodiments, the dielectric constant of the portions 140A, 140A′or 140B is greater than that of the dielectric layer 220. In someembodiments, the carbon concentration or content of the portions 140A,140A′ or 140B is less than that of the dielectric layer 220.

In some embodiments, the processes illustrated in FIGS. 1B-1G arerepeated one or more times to form one or more dielectric layers andconductive features. As a result, an interconnection structure includingmultiple dielectric layers and multiple conductive features is formedover the semiconductor substrate 100.

Embodiments of the disclosure provide a formation method of asemiconductor device structure. There are a first portion and a secondportion of the dielectric layer between conductive features. The firstportion surrounding one of the conductive features has a differentdielectric constant or carbon concentration than the second portion. Thesecond portion is subsequently modified to change its dielectricconstant or carbon concentration. Afterwards, the first and secondportions are removed by performing an etching process using a vapor toform a gap between the conductive features. As a result, sidewalls ofthe conductive features are prevented from being damaged during theformation of the gap. Since the second portion is modified and becomesremovable by the vapor, the size of the gap is increased. As a result,parasitic capacitance between the conductive features is mitigated oreliminated. Therefore, the RC delay of the semiconductor devicestructure is greatly reduced.

The modification is fine-tuned to accurately adjust the size and profileof the subsequently formed gap. The modification is also selectivelyperformed over the dielectric layer. It can be ensured that thedielectric layer with the gap provides sufficient support to theconductive features and other layers and features over the dielectriclayer. As a result, the gap is enlarged without severely degrading themechanical strength of the dielectric layer. Therefore, the deviceperformance and reliability of the semiconductor device structure issignificantly enhanced.

In some embodiments, the formation method shown in FIGS. 1A-1G is usedto form a gap between dual damascene structures in an interconnectionstructure of a semiconductor device structure. Many variations and/ormodifications can be made to embodiments of the disclosure. In someother embodiments, the formation method described in the disclosure canbe used to form a gap between single damascene structures in aninterconnection structure of a semiconductor device structure

Embodiments of the disclosure are not limited thereto. In some otherembodiments, the formation method described in the disclosure can beused to form any suitable opening in a dielectric layer.

In accordance with some embodiments, a method for forming asemiconductor device structure is provided. The method includes forminga dielectric layer over a semiconductor substrate. The method alsoincludes forming an opening in the dielectric layer. A dielectricconstant of a first portion of the dielectric layer is less than that ofa second portion of the dielectric layer surrounding the opening. Themethod further includes forming a conductive feature in the opening. Thesecond portion is between the first portion and the conductive feature.In addition, the method includes modifying an upper portion of the firstportion to increase the dielectric constant of the upper portion of thefirst portion. The method also includes removing the upper portion ofthe first portion and the second portion.

In accordance with some embodiments, a method for forming asemiconductor device structure is provided. The method includes forminga dielectric layer over a semiconductor substrate. The method alsoincludes forming a first opening and a second opening in the dielectriclayer. A first portion of the dielectric layer surrounds the firstopening. A second portion of the dielectric layer surrounds the secondopening. A dielectric constant of the first portion and a dielectricconstant of the second portion are changed during the formation of thefirst opening and the second opening. The method further includesrespectively forming a first conductive feature and a second conductivefeature in the first opening and the second opening. In addition, themethod includes modifying a third portion of the dielectric layerbetween the first portion and the second portion to change a dielectricconstant of the third portion. The method also includes removing thefirst portion, the second portion, and the third portion to form a gapbetween the first conductive feature and the second conductive feature.

In accordance with some embodiments, a semiconductor device structure isprovided. The semiconductor device structure includes a dielectric layerover a semiconductor substrate. The semiconductor device structure alsoincludes a first conductive feature in the dielectric layer. A portionof the dielectric layer has a top surface that is non-coplanar with atop surface of the first conductive feature. The semiconductor devicestructure further includes a second conductive feature in the dielectriclayer and extending from a bottom surface of the first conductivefeature. The portion of the dielectric layer is separated from thesecond conductive feature by a gap. A distance between the portion ofthe dielectric layer and the second conductive feature gradually becomessmaller along a direction from the top surface of the first conductivefeature towards the bottom surface of the first conductive feature.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method for forming a semiconductor device structure, comprising:forming a dielectric layer over a semiconductor substrate; forming anopening in the dielectric layer, wherein a dielectric constant of afirst portion of the dielectric layer is less than that of a secondportion of the dielectric layer surrounding the opening; forming aconductive feature in the opening, wherein the second portion is betweenthe first portion and the conductive feature; modifying an upper portionof the first portion to increase the dielectric constant of the upperportion of the first portion; and removing the upper portion of thefirst portion and the second portion.
 2. The method for forming asemiconductor device structure as claimed in claim 1, wherein the firstportion of the dielectric layer contains carbon, and the upper portionof the first portion is modified by partially removing carbon in theupper portion of the first portion.
 3. The method for forming asemiconductor device structure as claimed in claim 1, wherein the secondportion is between a lower portion of the first portion and theconductive feature, and a vapor is used to remove the upper portion ofthe first portion and the second portion, and the lower portion of thefirst portion is substantially not removed by the vapor.
 4. The methodfor forming a semiconductor device structure as claimed in claim 1,further comprising forming a mask layer over the dielectric layer andthe conductive feature before the modification, wherein the firstportion and the second portion are exposed from the mask layer.
 5. Themethod for forming a semiconductor device structure as claimed in claim4, wherein the dielectric constant of the upper portion of the firstportion is less than that of a third portion of the dielectric layerbefore the modification, and the third portion is adjacent to theconductive feature and is covered by the mask layer.
 6. The method forforming a semiconductor device structure as claimed in claim 1, furthercomprising forming a second dielectric layer over the dielectric layerand the conductive feature, wherein the dielectric constant of the upperportion of the first portion after the modification is greater than thatof the second dielectric layer.
 7. A method for forming a semiconductordevice structure, comprising: forming a dielectric layer over asemiconductor substrate; forming a first opening and a second opening inthe dielectric layer, wherein a first portion of the dielectric layersurrounds the first opening and a second portion of the dielectric layersurrounds the second opening, and a dielectric constant of the firstportion and a dielectric constant of the second portion are changedduring the formation of the first opening and the second opening;respectively forming a first conductive feature and a second conductivefeature in the first opening and the second opening; modifying a thirdportion of the dielectric layer between the first portion and the secondportion to change a dielectric constant of the third portion; andremoving the first portion, the second portion, and the third portion toform a gap between the first conductive feature and the secondconductive feature.
 8. The method for forming a semiconductor devicestructure as claimed in claim 7, wherein the dielectric constant of thefirst portion and the dielectric constant of the second portion areincreased during the formation of the first opening and the secondopening.
 9. The method for forming a semiconductor device structure asclaimed in claim 7, wherein the dielectric constant of the third portionis increased during the modification.
 10. The method for forming asemiconductor device structure as claimed in claim 7, wherein thedielectric constant of the third portion before the modification is lessthan the dielectric constant of the first portion and the dielectricconstant of the second portion.
 11. The method for forming asemiconductor device structure as claimed in claim 7, wherein thedielectric constant of the third portion after the modification issubstantially equal to the dielectric constant of the first portion andthe dielectric constant of the second portion.
 12. The method forforming a semiconductor device structure as claimed in claim 7, whereinthe modification comprises performing an oxygen-containing plasmaprocess over the first portion, the second portion, and the thirdportion. 13-20. (canceled)
 21. A method for forming a semiconductordevice structure, comprising: forming a dielectric layer over asemiconductor substrate; forming a first conductive feature in thedielectric layer; forming a second conductive feature in the dielectriclayer extending from a bottom surface of the first conductive feature,wherein a first portion of the dielectric layer surrounds the firstconductive feature and the second conductive feature, and wherein thefirst portion of the dielectric layer is sandwiched between the firstconductive feature and a second portion of the dielectric layer;reducing a carbon concentration of the second portion of the dielectriclayer; and removing the first portion and the second portion of thedielectric layer to form a gap in the dielectric layer.
 22. The methodfor forming a semiconductor device structure as claimed in claim 21,wherein the first portion of the dielectric layer is further sandwichedbetween the second conductive feature and a third portion of thedielectric layer, and wherein a carbon concentration of the thirdportion is not changed during the reduction of the carbon concentrationof the second portion.
 23. The method for forming a semiconductor devicestructure as claimed in claim 22, wherein a carbon concentration of thefirst portion is less than the carbon concentration of the third portionbefore the reduction of the carbon concentration of the second portion.24. The method for forming a semiconductor device structure as claimedin claim 22, wherein a distance between the third portion of thedielectric layer and the second conductive feature gradually becomessmaller along a direction from the first conductive feature towards thesecond conductive feature.
 25. The method for forming a semiconductordevice structure as claimed in claim 21, further comprising forming athird conductive feature in the dielectric layer, wherein the thirdconductive feature is separated from the first conductive feature by thegap, and wherein the gap has a width that is substantially equal to adistance between the first conductive feature and the third conductivefeature.
 26. The method for forming a semiconductor device structure asclaimed in claim 25, further comprising performing a clean treatmentover the third conductive feature after the reduction of the carbonconcentration of the second portion.
 27. The method for forming asemiconductor device structure as claimed in claim 21, wherein the firstportion of the dielectric layer is removable by a vapor before thereduction of the carbon concentration of the second portion, and whereinthe second portion of the dielectric layer becomes removable by thevapor during the reduction of the carbon concentration of the secondportion.
 28. The method for forming a semiconductor device structure asclaimed in claim 21, further comprising forming a mask layer over thedielectric layer before the reduction of the carbon concentration of thesecond portion, wherein the mask layer covers the first conductivefeature and exposes the first portion and the second portion of thedielectric layer during the reduction of the carbon concentration of thesecond portion.